The news that Canada's Cannabis Act, which legalises and regulates the sale of cannabis, and its use and possession by adults, had passed its final legislative hurdle, was somewhat overwhelmed by the day-to-day madness of global news in 2018. But you will hear a lot more about it as New Zealand edges towards its promised cannabis referendum.

It was evident as soon as the Trudeau government won election with legalisation on its manifesto that the experience there might prove to be a vital case study for other liberal democracies. And that it is even more true now. Canada has done a lot of the thinking for the rest of us.

I have an impending Matters of Substance feature on the cannabis referendum promised in Labour's support agreement with the Green Party. It wasn't something any of the governing parties campaigned on, but because New Zealand First has long (ostensibly anyway) favoured a referendum on the issue, it happened to be the point where all three could agree.

So the government is coming to this historic vote from a standing start. But this much we know: the referendum will be held in either 2019 (possibly in conjunction with local body elections and/or a voluntary euthanasia referendum) or 2020 (at the same time as the general election). The minister responsible is Andrew Little. Andrew Little told me that it was unlikely that there would be a fully worked-up law for the people to vote on, and that his sense is that the referendum will not be binding.

The first part there is problematic: "legalising cannabis" is an almost meaningless proposition. It might involve anything from removing penalties for use and possession (yes, I know, that's decriminalisation) to weed supermarkets on the high street. People need to know what they're voting for. That's why the full text of California's successful Proposition 64 in 2016 ran to more than 100,000 words of legal and technical definitions. Almost no voters actually read it, but they wanted it to be there. New Zealand voters will feel the same.

So how much of our homework has Canada done for us? Parts of its law do not apply to us: principally, the decision to devolve some of the regulation to its provinces. But even that offers us options to look at. In Alberta, about 200 regulated private retailers will be allowed to sell cannabis – while Ontario will only allow 40 state-run weed stores. (I'm told by an Ontario friend that the provincial government's decision is not popular with voters, and the rules there might loosen with the next election.)

This Guardian explainer usefully rattles through other key issues: product labelling, public possession limits, a new, stricter drug-driving law (it's still an incredibly fraught area and will be until there's an efficient, reliable impairment test), limits for home-growing (four plants up to a metre high, except in Quebec or Manitoba, where it will remain illegal), edibles (can't be sold until the government works out some specific regulation some time next year) and the rights of landlords and employers to restrict consumption.

The provisions come come from A Framework for the Legalisation and Regulation of Cannabis in Canada, which is the final report of the taskforce appointed by the goverment to travel around the country and consult. There are many other recommendations in the report, including strong restrictions on advertising and higher taxes on higher-THC products.

It also proposed an age for legal adult use: 18.

The choice of 18 as a threshold has been controversial in Canada. We know that while heavy use is less risky at age 18 than it is at age 15, risk is lower still at 25, when brain development has stabilised and neuroplasticity is much less of an issue. In choosing the lower age, the task force concluded that:

... persons under the age of 25 represent the segment of the population most likely to consume cannabis and to be charged with a cannabis possession offence, and in view of the Government's intention to move away from a system that criminalizes the use of cannabis, it is important in setting a minimum age that we do not disadvantage this population.

Anne McLellan, the former Canadian deputy Prime Minister who led the task force defended the choice of 18 in similar terms when she visited New Zealand last year: yes, you could minimise risk by opting for 25, but that would marginalise the very group of users you’re trying to engage and educate. She made the point that Canada was reforming precisely because the rate of youth use had remained worryingly and persistently high under prohibition.

It's worth noting that New Zealand doesn't currently have a minimum age for cannabis use. It also doesn't have any official guidelines for lowering the risk of cannabis use. Canada does, having adopted this 2017 expert literature literature review. It offers 10 key points:

For most recommendations, there was at least “substantial” (i.e., good-quality) evidence. We developed 10 major recommendations for lower-risk use: (1) the most effective way to avoid cannabis use–related health risks is abstinence, (2) avoid early age initiation of cannabis use (i.e., definitively before the age of 16 years), (3) choose low-potency tetrahydrocannabinol (THC) or balanced THC-to-cannabidiol (CBD)–ratio cannabis products, (4) abstain from using synthetic cannabinoids, (5) avoid combusted cannabis inhalation and give preference to nonsmoking use methods, (6) avoid deep or other risky inhalation practices, (7) avoid high-frequency (e.g., daily or near-daily) cannabis use, (8) abstain from cannabis-impaired driving, (9) populations at higher risk for cannabis use–related health problems should avoid use altogether, and (10) avoid combining previously mentioned risk behaviors (e.g., early initiation and high-frequency use).

Some of these are difficult or impossible to apply in a prohibitive environment.

Canada has taken another important step: making clear that a past cannabis conviction will not be a barrier to joining the new, legal and regulated cannabis industry. I think this will be important to Māori communities who have suffered grossly disproportionate criminalisation for decades.

Canada has yet to decide whether it will follow California in expunging historic convictions for offences which no longer apply. Andrew Little was a little startled when I put it to him that it could be part of the package here, but our prosecution of cannabis laws has been as racially inequitable as California's has. This is a chance to redress enduring historic wrongs. It is also wholly in line with Little's own ideas about criminal justice reform.

So anyway, there is much to discuss and not much time to discuss it in – a public engagement programme can't even roll out until it receives funding in next year's Budget. And give that time is tight, we should be watching our Commonwealth cousins closely – and let Canada do our cannabis homework.

Colorado got a few things wrong – allowing over-dosed edibles packaged like kids’ candy was never a good idea – but they’ve continued to pay attention and tweaked regulations as required. Their regulators and legislators seem motivated by evidence rather than scare stories.

On the other hand, I think California’s provision for the expungement of old convictions is the new benchmark for reform.

And I like that Canada is addressing the potential problem of Big Cannabis – the task force report covers diversity in the production sector. It’ll be interesting to see how their "micro” licences for craft producers turn out. It’s probably not something you'd see in capitalist America, but it could be a good solution,

The Canadian system seems pretty chaotic at the moment, mainly because each state can decide its own laws. As Russell points out above, some states intend to allow users to grow their own modest crops, while other states will expressly forbid this. Some states encourage local businesses, while others have created a free-for-all where big money will be allowed to dominate the market, effectively knocking out existing, smaller producers.

While I welcome the possibility of seeing weed legalised in NZ in my lifetime, I'd hate to see either big tobacco or big pharma control the local industry. You just need to look at what's happening in Oregon to see how that might go.

As a better starting point for NZ, why not consider the Drug Foundation's draft policy, which appears to be based on a common sense, health-based approach to drugs.

As I recall the Drug Foundation supports the concept of small-scale growers all over the country, with centralised sales being restricted to a single government website. This would bring jobs to the regions, tax is calculated and collected at the point of sale and no corner dairies get robbed in the process.

I'm sure we'll be looking closely at the Canadian experience, but hopefully with enough nouse to keep it kiwi wherever possible.

while others have created a free-for-all where big money will be allowed to dominate the market, effectively knocking out existing, smaller producers.

As I noted above, it'll be interesting to see how the "micro" licences announced only a week ago turn out. And I get the impression that some of the more controlling regulations noted your link just won't be viable – making everyone deliver to a central warehouse before distribution to stores just seems dumb.

I’d hate to see either big tobacco or big pharma control the local industry. You just need to look at what’s happening in Oregon to see how that might go.

Yeah. There’s been some criticism of the tight regulation in the Canadian law – which controls who can grow and how much – but the American approach has its problems too. Cannabis is, as Sanho Tree likes to note, a minimally-processed agricultural commodity. The US experience suggests the unregulated price floor is very low indeed, and gets lower if you allow mass production to dominate and kill off your small growers.

Snapshots from the past...Back in the ’70s Vancouver’s Georgia Straight and their resident comic and cover artist Rand Holmes contributed mightily in the push for changes to marijuana laws.(Above: – Harold Hedd comics and the coin Holmes designed to commemorate legalising Medical Marijuana back in 2001

Thanks Russell, good appraisal & I agree we ought to get past convictions scrubbed (even if most such convicts are probably now dead).

Let's keep an open mind re the current Minister of Justice. Binding would be best, but if he designs one that has suitable text - to produce a mandate for subsequent legislation - he'll deserve our respect.

I agree with Alfie & the Drug Foundation that users must be able to grow their own. Canada setting four plants per person could be a problem: gardeners know plenty of seedlings get wiped out by nature before getting established. If the legislation specifies four fully-grown plants, no problem.

I agree that teenage users get damaged, but they'll use it anyway - so a twenty anything age discrimination law will never work. Jeez, I recall one of my younger brothers telling me he & school-friends were getting high & I warned him accordingly. That was 1971, Wanganui (he was 16). As a result he's been straight & extremely hostile to drug-taking since the early eighties. Zillions of similar stories around the world since then provide a substantial common ground of experience.

Sceptics point to the lack of evidence of any conception opportunity in March '71. Common sense tells us that any such tryst was designed to be secret, of course! Anyone who looks at the faces of the contending fathers & son can see at a glance who the real father is. No scientic basis for the inheritance of charisma (yet) but I can see where he gets it...

Girls just wanna have fun. She went on to author four books, was actress, photographer, tv talkshow hostess, got awarded an honorary Doctor of Laws from a university in Ontario. Tours giving talks on bipolar - wonder if she opines on the tendency of certain drugs to escalate that predisposition...

Ontario has just elected a provincial conservative government. I suspect that there may be setbacks there, although the current Premier Doug Ford's late brother Rob Ford was an infamous polydrug user while he was Toronto Mayor, especially crack cocaine.

An interesting study about the use of cannabis products for relieving chronic pain. I don't think it quite says what the Sydney Morning Herald thinks it does. The full report is available from the Cochrane link.

TL;DR Study says

The potential benefits of cannabis-based medicine (herbal cannabis, plant-derived or synthetic THC, THC/CBD oromucosal spray) in chronic neuropathic pain might be outweighed by their potential harms. The quality of evidence for pain relief outcomes reflects the exclusion of participants with a history of substance abuse and other significant comorbidities from the studies, together with their small sample sizes.

but that cannabis products performed higher than placebos.

The SMH says

Cannabis' medical benefits have suffered a serious blow, with a major study finding it does almost nothing to help people with chronic pain.

The study, one of the largest and most in depth ever done on the drug’s medical use, found cannabis does not cut pain, nor does it help sufferers replace opioids. And users seem to suffer higher levels of anxiety overall.

I thought the most interesting bit from the SMH was this: "the results are not straightforward. Most of the cannabis users reported they personally felt it worked well to treat their pain – despite also reporting higher levels of pain."

A paradox, requiring interpretation. Most users got pain relief from their usage, but it was temporary, because the cause of their pain was not removed. If you treat symptoms instead of causes, you fail to solve the problem. Science, when used by the media as a smokescreen, produces disinformation.

Healing ought to be the focus. Merely managing patients institutionalises a high-cost health system. Science applied to medicine via statistics has an unfortunate tendency to lead to banal generalisations, as in this instance. Running regularly makes many people more healthy but we don't force everyone to do it because it doesn't work for many others. The reason people need the law changed is because it produces a better quality of life for many, and that evidence comes from personal testimony, not stats. Dismissing it as hearsay is traditional science and bad public policy!!

Deb Lynch, president of the Medical Cannabis Users Association: “It has given me back my life. Prior to starting on the oil treatments, I was on high doses of multiple opiates. I was in bed wanting to kill myself and my pain wasn’t being addressed. Now I’m running all over the country.”

It's worth noting that this paper was based on an evaluation of 16 previous studies, the quality of which was variable to say the least.

We rated the quality of the evidence from studies using four levels: very low, low, moderate, or high. Very low-quality evidence means that we are very uncertain about the results. High-quality evidence means that we are very confident in the results.

There was no high-quality evidence.

I'm sure the work was well-intentioned, however it appears that neither the source nor the strains of cannabis were taken into account. While some patients may have been using high-quality CBD strains, others could have been consuming rough as guts bush weed. This omission lacks scientific rigour.

And more importantly, the SMH report implies that the participants continued to use opiods throughout the process, concluding "It did not help them cut their opiod use at all." Is it even possible to assess the effectiveness of cannabis to treat pain when all of the subjects are simultaneously consuming other serious painkillers?

Recording degrees of pain (on a scale of one to ten) is always subjective but as it apparently increased for the majority of participants, you could just as easily hypothesise that this study proves opiods decrease in effectiveness over time.

For years, the illegality of cannabis has restricted scientific research into its healing properties. While high quality studies are undoubtably needed, this does not appear to be one of them. It's unfortunate that certain sections of the media feel empowered to draw their own conclusions because, well... clickbait.

Medicinal cannabis users of my acquaintance who use the drug as an alternative to opiods claim it's effective in pain management with far fewer side effects, if any. As a bonus they sleep better and are happier most of the time. Dennis is correct in saying that quality of life must be taken into account and should inform policy.

Medicinal cannabis users of my acquaintance who use the drug as an alternative to opiods claim it’s effective in pain management with far fewer side effects, if any.

I’m noticing this cannabis is anecdotally better than opioids for pain management argument starting to be used frequently. I don’t think it’s a good comparison. For example, if someone runs there motorcycle under a truck and trailer unit and make it out the other side alive but with serious injurys, the ambulance staff will often administor morphine. This would no be to kill pain. It would be to help the traumatised person with the broken bone sticking out of the leg to be more emotionally able to deal with it. Opioids are good for that. Cannabis is probably not.

If I was going to make comparisons, I’d say alcohol and opioids. And not just because theres proper biological science to say they act on us in a closely related way, it’s also that I’ve known alcoholic drug addicts who say it’s true.

Mabe cannabis is complementary to opioids in a pain management plan. Mabe cannabis is more appropriate than opiates because opioids where inappropriate and the addiction sickness was more debilitating than the other pain it was intended to treat. Mabe, that’s mabe, because there really truly actually isn’t enough science. unfortunately.

Israel is probably a good place to keep an eye on as the medical cannabis science starts to develop. It’s been happening there more than most other places.